Sedative, analgesic and cognitive effects of clonidine infusions in humans†  J.E. Hall, T.D. Uhrich, T.J. Ebert  British Journal of Anaesthesia  Volume 86, Issue 1, Pages 5-11 (January 2001) DOI: 10.1093/bja/86.1.5 Copyright © 2001 British Journal of Anaesthesia Terms and Conditions

Fig 1 Group results (means) of bispectral index (BIS) numbers recorded every 5 min during the 60 min infusion and 90 min recovery periods in eight volunteers. British Journal of Anaesthesia 2001 86, 5-11DOI: (10.1093/bja/86.1.5) Copyright © 2001 British Journal of Anaesthesia Terms and Conditions

Fig 2 Results of sedation tests indicate that there were progressive increases in sedation with increasing dose of clonidine. There were significant differences by ReANOVA (†) compared with placebo for the 2 and 4 μg kg−1 h−1 doses for all tests of sedation. In addition, specific time points were compared with baseline with Bonferroni post hoc analysis *P<0.05. British Journal of Anaesthesia 2001 86, 5-11DOI: (10.1093/bja/86.1.5) Copyright © 2001 British Journal of Anaesthesia Terms and Conditions

Fig 3 (Upper graph) Percentages of words recalled in the three 16-word memory tests given at baseline, after 60 min of infusion and 45 min into recovery. Only the clonidine 4 μg kg−1 h−1 infusion resulted in significant impairment in memory. *p<0.05 compared to placebo. (Lower graph) The 90 min recovery comprehensive memory test, in which subjects were asked to recall as many of the words as possible from the lists presented previously. The total number of recalled words and the list from which the word originated are shown. The total number of words recalled was greatest in the placebo group, whose recall increased from baseline, so that the most words were recalled from the most recent list. This progression did not persist in the clonidine groups, primarily because of the volunteers’ inability to recall words presented during the infusion periods. This was particularly true during the 4 μg kg−1 h−1 infusion, when only two (of 16) words were recalled. †P<0.05 compared to placebo. British Journal of Anaesthesia 2001 86, 5-11DOI: (10.1093/bja/86.1.5) Copyright © 2001 British Journal of Anaesthesia Terms and Conditions

Fig 4 Visual analogue scale (VAS) for coordination, as evaluated by the volunteers, and the 90 s timed digital symbol substitution test (DSST). Significant impairment was found in the clonidine 4 μg kg−1 h−1 group, but no significant changes were seen in the other groups. †Results of ReANOVA; *comparison of specific time points from baseline responses (P<0.05). British Journal of Anaesthesia 2001 86, 5-11DOI: (10.1093/bja/86.1.5) Copyright © 2001 British Journal of Anaesthesia Terms and Conditions

Fig 5 With increasing doses of clonidine, there was a trend for the cold pressor test to elicit smaller increases in mean arterial blood pressure and pain scores. Significance was achieved, in terms of reduction in blood pressure and the pain response, at the 4 μg kg−1 h−1 infusion rate (*P<0.05). The attenuation of the arterial pressure response and the pain response persisted through 45 min of recovery. †Significant difference between groups. British Journal of Anaesthesia 2001 86, 5-11DOI: (10.1093/bja/86.1.5) Copyright © 2001 British Journal of Anaesthesia Terms and Conditions

Fig 6 The haemodynamic responses to infusion of clonidine and placebo. The data suggest that clonidine lowered arterial pressure whereas placebo raised it, but statistically significant differences were not achieved between groups during the infusion periods. Similarly, heart rate showed no significant changes over time compared with baseline. *P<0.05 compared to baseline. British Journal of Anaesthesia 2001 86, 5-11DOI: (10.1093/bja/86.1.5) Copyright © 2001 British Journal of Anaesthesia Terms and Conditions